Method of sheathing cable cores



March 3, 1953 A. N. GRAY 1 METHOD OF SHEATHING- CABLE CORES Filed Feb.4, 1950 FIG INVENTOR F/G. 2 A N GRAY ATTORNEY nn nn V444 .4

Patented Mar. 3, 1953 UNITED STATES. PATENT OFFICE METHOD OF SHEATHING-CABLE CORES Alvin NZ 'GrayyEdgewood, Md.,. assignorto West em ElectricCompany, Incorporated, New York, N. Y., a corporation of New YorkApplication February 4, 1950, Serial No. 142,514

1 Claim; (Cl. 29-448) used in the communications field, it sometimes isdesirable to apply a protective covering of' vulcanlzed rubber orrubber-like compound around the lead sheath. Usually the covering isapplied around a lead sheath by an extrudingapparatus', and i vulcanizedthereafter by advancing the covered cable through an elongatedvulcanizing tube containing high pressure, high temperaturesteam. Sincethe cable core must be kept in a dry condition to maintain theinsulation of the individual conductors eflective, it isnecessary toseal the ends of the cable before it passes through the vulcanizing tubeto prevent the steam from entering and damaging the insulation of theconductors.

An object of the invention i to provide new and improved methods ofsheathing cable cores. Another object of the invention is to providenewand improved methods'of sheathing cable cores so that they may beadvanced through vulcanizing apparatus.

A method of sheathing multi-conductor cable cores embodying certainfeatures of the invention comprises securing a cap to one end of thecable core, and extruding a lead sheath over the cable core so that thesheath adherestothe cap to form a tight seal therewith.

A complete understanding of the invention may be had from the followingdetailed description of specific embodiments thereof, when read inconjunction with the appended. drawing, in which:

Fig. 1 is a fragmentary, partially sectional view of a. multi-conductorcable which may be manufactured by methods embodying certain features ofthe invention, and

Fig. 2 is a fragmentary view of the cable; shown in Fig. 1 during onestage of its fabrication.

Referring now to Fig. 1, there is shown an end portion of a completedcable ID of a type generally used in the communication field fortransmitting telephone messages over long distances. The cable Iincludes a composite core ll which includes a plurality of individuallyinsulated con-,

ductors |2-l2 twisted together a predetermined group and having severallavers of paper tape |3l3 served spirally around the group ofconductors. The core II is enclosed in a thin lead sheath l5, which inturn, is covered by a.

heavy jacket I 6 of a suitable vulcanizable compound, such as rubber, orsynthetic rubber-like compounds.

A cup shaped cap 20 preferably composed of lead or a lead alloy issecured to the end of the cable core H, and the lead sheath I5 appliedover the core ll encloses a sleeve portion 19 of the cap and is fusedthereto. The cap seal the end of the cable to prevent entrance of highpressure, high temperature steam used to vulcanize' the jacket l6 intothe cable core. An eyebolt 2i secured to the end of the cable core Ilmay be attached to a chain, a cable or other pulling instrumentality topull the cable Whenever necessary in forming the sheath [5 and thejacket Miami in installing the cable in a conduit or a. trough.

In applying and sheathing the core I I, the core usually is coiled on asuitable reel and placed in a conventional drying oven for a givenperiod of time in order to remove excess moisture from the insulationsurrounding the individual conductors of the cable core. When the cablecore H is dry, the paper tape I3 is stripped from one end of the cablecore II for a predetermined distance suiiicient to permit the end of thecore to be prepared to fit into the cap 20. The end portions of some ofthe conductors I2l2 at the end'of' the cable are cut away to form areduced end portion 25 of the core which fits into the cap 20' with apredetermined clearance between the core and the cap. The insulationsurrounding the individual conductors of the reduced portion 25 of thecore II i removed along the reduced portion 25, and the shank of theeyebolt H is passed through a bore 22 provided in the end of the cap 20,and is inserted into the center of the core to'the position thereofshown in Fig. 2. The bare conductors l2-l2 near the center of the coreare first soldered to the eyebolt 2|, and the bared end portions of theremaining conductors are soldered together layer by layer until all theconductors are soldered together.

' After the eyebolt is soldered to the end of the core H, in thismanner, the lead cap 20 is filled partially with a molten lead, or asuitable lead alloy, and is positioned over the end of the cable core Il to a position in which the end of the cap abuts a shoulder 30 of thecable core. The cap carries molten metal 23 around the reduced portionof the core H so that this end of the core is completely surrounded bythe molten metal. When the molten metal 23 solidifies, the cap 20 iswelded securely to the end of the cable core and the bore 22 is sealedhermetically against entrance of high pressure fluids by the metal 23which has flowed into the bore 22 as the cap is moved into the positionshown in Fig. 1.

After the cap 20 has been secured to the end of the cable core II inthis manner, the other end of the cable core is capped identically withthe capping described hereinabove, and the end of the cable is withdrawnfrom the reel positioned in the oven and advanced through a continuouslead extruding apparatus of a well known type which form the thin leadsheath [5 around the core II and the sleeve portions of the caps. Theoutside diameter of the sleeve portion IQ of the cap is substantiallythe same as that of the core I I so that the cap may be advanced throughthe lead extruding apparatus. is formed of hot lead in a plasticcondition, and

The lead sheath 4 end thereof, may be withdrawn from its storage reeland advanced through the lead extruding apparatus, and thereafter coiledup on another cable reel. The sheathed cable core may be stored for anindefinite time without acquiring moisture, or it may be transported inreeled condition directly from the lead extruding apparatus to theapparatus designed to apply the rubber adherent compound to the leadsheath. The adhesive compound applying apparatus, the extrudingapparatus, the vulcanizing tube and the cooling apparatus may bepositioned in tandem. since it is desirable to extrude the vulcanizingcompound over the lead sheath immediately after the rubber adherentcompound is applied. This procedure is well suited to factory conditionswelds itself to the sleeve portion of the lead caps on the ends of thecore to form pressure-tight,

seals on the ends of the cable core ll.

. One type of an apparatus which may be used for extruding the leadsheath 15 around the core II is known as a Pirelli lead press which isdescribed fully on pages 319 to 324, inclusive, of the issue of theBritish publication Engineering, published April 8, 1949.

The cable core having the sheath l5 thereon is passed through a suitableapparatus designed to apply a rubber and lead adherent compound on thesheath I5. One type of rubber adherent compound, which may be used forpurposes of this invention, is described in T. K. Cox et a1. Patent2,393,024, issued January 15, 1946. Apparatus similar to that shown inPatent 2,393,024 may be used to apply the rubber adherent compound onthe lead sheath of the cable Ill.

Immediately after the application of the rubber adherent compound, thecapped and sheathed cable core is advanced directly through an extrudingapparatus of a well known type, which extrudes the heavy jacket N3 ofthe vulcanizable compound, such as a rubber compound, or a syntheticrubber-like compound, over the lead sheath IS. The jacketed core isadvanced continuously and directly from the extruding apparatus into andthrough an elongated vulcanizing tube filled with a high temperature,high pressure vulcanizing fluid, such as high pressure, high temperaturesteam. The vulcanizing fluid heats the jacket under suilieient pressureto vulcanize the jacket. The rubber and lead adherent compound appliedon the sheath, reacts with the vulcanizable compound during thevulcaniza tion process so as to bind the vulcanized jacket [6 securelyto the lead sheath. As the cable I3 leaves the tube containing thevulcanizing fluid, it passes directly through a low temperature fluid,such as low temperature water, to cool the vulcanized jacket l6, andthereafter the completed cable I!) is coiled up on a takeup reel. Thecaps -20 hermetically sealed to the lead sheath, prevent the fluid usedin the vulcanizing tube and the cooling fluid from entering and damagingthe insulation of the individual conductors of the core I I.

One type of apparatus that may be used to extrude the vulcanizablecompound cover around the lead sheath of the cable it! and to vulcanizethe jacket I5 is described in G. L. Cherry Patent 1,770,969 issued July22, 1930.

The above-described steps in the manufacture of the cable ID also may becarried out with interruptions between the several steps as well ascontinuously. For example, a given length of the core II, having a cap20 secured on each which prevent the manufacture of such cables by acontinuous process due to the floor space requiredto carry out such aprocess.

To manufacture such cables by a substantially continuous process, thelead extruding apparatus, the apparatus for applying the rubber and leadadherent compound, the compound extruding apparatus, the vulcanizingtube, the cooling apparatus and the takeup apparatus are positioned intandem in the order named. One or more capstans usually are positionedat suitable points in the tandem arrangement to advance the cable coreand the finished cable through the apparatus. In this arrangement, atthe start, the cable core is pulled through the apparatus by a suitablechain or rope attached to the eyebolt 2| secured to the forward end ofthe cable core until it is engaged by the capstans provided foradvancing the cable through the apparatus. When the trailing end of thefirst length of a cable core, like the core ll, leaves its supply reel,it is connected to the leading end of another length of the same type ofcable core by a short length of chain or wire rope so that the cablecore being advanced through the lead press, the apparatus for applyingthe rubber adherent compound and the compound extruding apparatus willpull the next length of cable through the apparatus. This arrangement ofthe eyebolts secured to the ends of the cable cores facilitates using asubstantially continuous process of manufacturing the cable ID.

The cap 20 secured on the end of the cable and covered by the leadsheath l5 produces a pressure tight seal on the end of the cableimpervious to air and moisture, thereby preventing infiltration of airand moisture into the cable while the cable is stored. The eyebolt 2| issoldered to the core H in the manner described? so that when the'eyebolt is used to'pull' the cable or core all of the pull istransmitted to the core to which molten lead will adhere readily.

While the above-described method of sealing" the ends of a cable core sothat it may be ad: vanced through conventional vulcanizing apparatus isparticularly suitable for manufacturing multiyconductor telephonecables, it may be readily adapted to seal the end of other. types ofcable cores without departing fromthe spirit: and scope or theinvention.

What is claimed is:

The method of sheathing insulated cable cores, which comprises the stepsof cutting both ends of a cable core to form portions of reduced size,soldering to each end of the cable core a shank of an eyebolt whichextends through a bore in a cap, pouring molten lead into each cap untilit is partially full, positioning the caps abutting the ends of thecable core so that the molten lead will secure the caps to the reducedends of the cable core, linking a series of such capped cable corestogether end to end by means of their eyebolts, and continuouslyadvancing the series of cable cores through a lead press, a rubberextruder. and a tube containing a vulcanizing fluid under hightemperature and high .pressure all arranged in tandem to applysequentially a continuous lead sheath over the cable core and acontinuous, vulcanized rubber covering over the lead sheath.

ALVIN N. GRAY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

